As far as the parental demands and such, that sounds like another problem altogether.
As oppose to having to spend more to accomodate the (parenting)problem, it sounds like the problem itself needs to be dealt with. (I don't want to make suggestions because that would likely take us way off topic).

I have searched for reliable data present and it seems to be fairly difficult to organize on costs per pupil for different countries (all the numbers I found were taking different things into account.).
The things that did remain constant is that we spend considerably more and the results are considerably less. I don't believe that can be argued with.
Can you identify a country out there that spends more and performs worse?
Something is definitely wrong.
Perhaps it is our society. Maybe "everyone gets a trophy" and "nobody loses" when kids are growing up is to blame. I don't know. I just KNOW that we waste alot of money on poor results. I don't think it is fair and I believe parents need more choices. As in the free market, choices yield better products/services/VALUE. Am I mistaken?

With a comparison of school cost with other countries, one compares apples with pears. The US public school sytem has to "mainstream" all students, no matter how complicated their handicap is. This is not the case in many other countries. In many countries, kids with a handicap get placed special Institutions (where they may or may not get an education). The PISA study (the one that compares schools and their achievements) will not consider these kids in those countries, because they are not in a school. However, in the US those kids are part of the school system and are included in the rating. Not only reduces this the statistical outcome, but it also increases the cost per student. many of the handicapped kids have an assistant during the entire school day, and very often there are only five students per teacher.

Any cost and outcome comparison between the US school system and that of many other countries is useless because of the different conditions.

If one compares public schools with private schools, the picture is also distorted. Public schools have to take any student, private schools can select who they take!
I am a member of the school board of a charter school, and I can tell you that this school tests each student prior to admitting the student to this school. We have a very high outcome in this school! We can do this, because we are a charter school, a public school is not allowed to do this!

The only real comparison that can be made is between the identical school systems, i.e between public schools and between private schools.

With those comparisons it is a pretty well know fact that schools in northern states have generally a better outcome results than schools in southern states. The best outcome results are mostly found in the schools in Minnesota and Wisconsin. Herewith, the questions should be, why is that so?

My wife is a professor at a grad school of education, and she educates master teacher candidates from all over the US. She also knows that her peers at other universities have similar teachings. This means, almost all teachers in the US get a similar education for their profession, and yet you see a outcome difference between north and south.

Why is this, what is the reason for this?

This is the area that should be analysed! If all schools in the US would have similar outcomes as the ones in the northern states, the statistical outcome for the public school system in the US would be by far better than it is now!

There are some truly wonderful public school districts that do a great job of churning out roundly-educated high school graduates. There are also some truly awful ones that have a dismal graduation rate of 50% or less. Most of those schools with lousy grad rates are in urban areas catering to lower-income kids. Based on personal observation, the single biggest issue is lack of parent involvement or the parents even caring whether their little darlings even show up for class. Money isn't the problem, nor are resources or teachers.

My son currently attends a private school that costs $7400/year which is substantially less than the amount spent on public school students on average. I mention this only to highlight that a lack of money isn't the problem.

So while graduation rates in nicer suburban schools might be at or close to 100%, I'd probably opt to send my kids to a public school if its academic programs were comparable to those of private schools I could afford. But if I lived in a district with less-than-desirable schools, I'd take advantage of the voucher if it were available.

As for parents settling for a worse education for their kids in order that schools not go under or that special-needs kids have the funding they need, I can't go along with that. Altruism and I don't get along.

One huge problem noted by many teacher friends of mine is the absurd policy of mainstreaming special needs kids in with regular classes. This doesn't help anyone.

freakonomics, you should read it, the quality of the high school has little do to do with the outcome of the student, There was a lottery where some students from the worse schools could opt-in to the lottery for the "better" schools, of the ones that opted in which ones faired better post high school the ones that went to the better school or the ones stuck in the bad school? neither, the ones that faired better were the ones that opted for lottery for the better schools

(I know I said faired instead of specifics, I read it a while ago, but I am pretty sure it was referring to the college acceptance or graduation rate....)

With a comparison of school cost with other countries, one compares apples with pears. The US public school sytem has to "mainstream" all students, no matter how complicated their handicap is. This is not the case in many other countries. In many countries, kids with a handicap get placed special Institutions (where they may or may not get an education). The PISA study (the one that compares schools and their achievements) will not consider these kids in those countries, because they are not in a school. However, in the US those kids are part of the school system and are included in the rating. Not only reduces this the statistical outcome, but it also increases the cost per student. many of the handicapped kids have an assistant during the entire school day, and very often there are only five students per teacher.

Any cost and outcome comparison between the US school system and that of many other countries is useless because of the different conditions.

If one compares public schools with private schools, the picture is also distorted. Public schools have to take any student, private schools can select who they take!
I am a member of the school board of a charter school, and I can tell you that this school tests each student prior to admitting the student to this school. We have a very high outcome in this school! We can do this, because we are a charter school, a public school is not allowed to do this!

The only real comparison that can be made is between the identical school systems, i.e between public schools and between private schools.

With those comparisons it is a pretty well know fact that schools in northern states have generally a better outcome results than schools in southern states. The best outcome results are mostly found in the schools in Minnesota and Wisconsin. Herewith, the questions should be, why is that so?

My wife is a professor at a grad school of education, and she educates master teacher candidates from all over the US. She also knows that her peers at other universities have similar teachings. This means, almost all teachers in the US get a similar education for their profession, and yet you see a outcome difference between north and south.

Why is this, what is the reason for this?

This is the area that should be analysed! If all schools in the US would have similar outcomes as the ones in the northern states, the statistical outcome for the public school system in the US would be by far better than it is now!

I believe you make some very valid points. I think it is very difficult (impossible?) to compare apples to apples between countries.
I do think that there are likely explanations for the disparities between north and south. I don't know what they are, it would be interesting to know.

The one thing that I do see in common between the top 5 performing states, is that they are among the 10 smallest states in the union (whether that has ANY meaning at all I don't know).

I just believe that some sort of voucher program would be great. I would like to have enough money to possibly select a private school, or homeschool but whatever expense I would have associated with those would be IN ADDITION to my "expenses" to fund my childs public education.